By way of examples in the prior art, US 2003/0131599 discloses air-storage power stations in which a compressor compresses air in times in which the electricity demand is low, and feeds this to a storage volume. The air stored there is expanded, producing work, in times of high electricity demand, in an expansion machine, for example a turbine. In this case, the expansion machine drives a generator which supplies power to an electrical grid system. Power stations such as these are particularly suitable for the regulation of the power consumption and emission in an electrical grid system. In the charging mode, in which the compressor is operated, the power consumption of the compressor can be reduced by a constriction, and can thus be matched to a rising power demand in the grid system. In the power mode, in which the expansion machine is operated, the power emission from the expansion machine can be matched by a different constriction of the storage fluid flowing to it and, if required, by a different amount of power from a furnace system to the power demand from the grid system. An electric motor which is used to drive the compressor and a generator which is driven by the expansion machine are rigidly connected, that is to say at a synchronous frequency, to the electrical grid system. The expansion machine and the compressor are thus operated at a constant rotation speed. A turbine which is used as the expansion machine and/or a turbo compressor are then operated at different mass flow levels away from their best operating point. Furthermore, the constriction of flow to the compressor is highly lossy. It should also be remembered that the generator cannot be connected to the grid system, and cannot supply power, until after the expansion machine has been accelerated to the synchronous rotation speed for the grid system.